Modular scheduling of distributed heterogeneous time-triggered automotive systems

Abstract

This paper proposes a modular framework that enables a scheduling for time-triggered distributed embedded systems. The framework provides a symbolic representation that is used by an Integer Linear Programming (ILP) solver to determine a schedule that respects all bus and processor constraints as well as end-to-end timing constraints. Unlike other approaches, the proposed technique complies with automotive specific requirements at system-level and is fully extensible. Formulations for common time-triggered automotive operating systems and bus systems are presented. The proposed model supports the automotive bus systems FlexRay 2.1 and 3.0. For the operating systems, formulations for an eCosbased non-preemptive component and a preemptive OSEKtime operating system are introduced. A case study from the automotive domain gives evidence of the applicability of the proposed approach by scheduling multiple distributed control functions concurrently. Finally, a scalability analysis is carried out with synthetic test cases.

Schedule Integration Framework for Time-Triggered Automotive Architectures

“…Hence, the testing and analysis required to validate correct system behavior is significantly reduced. On the other hand, the design complexity for time-triggered systems typically grows exponentially if a system schedule is generated from the scratch, see [9] [11]. As a remedy, our schedule inte- gration exploits the predictability of time-triggered systems.…”

“…As the focus here lies on schedule integration, please refer to [11] for the ILP formulation to determine a feasible schedule. Depending on the application requirements, an optimization objective might be defined for a minimal end-to-end delay [7], the control performance [13], or the extensibility to ease later schedule integration [14].…”

“…Constraints (11) and (12) then define the range for each process. We distinguish three cases: (a) The process is a source or a sink process and can only be shifted in right or left direction, respectively, reducing the end-to-end delay but not increasing it.…”

“…An Satisfiability Modulo Theories (SMT)-based approach to generate time-triggered schedules for TTEthernet is presented in [10]. Finally, two Integer Linear Programming (ILP)-based approaches have been presented for the FlexRay bus in [7] [11]. While [7] addresses the problem at joblevel, [11] applies the schedule optimization at task-level.…”

“…Finally, two Integer Linear Programming (ILP)-based approaches have been presented for the FlexRay bus in [7] [11]. While [7] addresses the problem at joblevel, [11] applies the schedule optimization at task-level. Most of these approaches perform well for small subsystem schedules, but do not scale well for larger systems.…”